Structural support systems, such as those used in buildings or bridges, often incorporate steel girders to form a load-carrying element. For instance, in the case of bridges, the generally horizontally extending girders provide support to an overlying superstructure (e.g., a bridge deck) and transfer loads to support columns or other structures anchored to the ground. Girders have a variety of cross-sectional configurations, such as I-beam and box-shaped, each providing specific advantages depending on the particular design parameters for a load carrying system. In certain situations, for example, it is desirable to maximize the strength-to-weight ratio for a girder design, while other situations dictate the incorporation of girders that are, above other considerations, easy to fabricate with low maintenance over time.
Despite advances in design for load carrying systems, conventional fabrication methods for steel girders are still generally labor intensive, and result in a finished product that is relatively expensive. With both I-beam and box girder configurations, for example, there is a large amount of welding that must be done to secure the main structural components of the girder together. Furthermore, because of the extent of welding that is necessary, there is frequently a long delay introduced from the time a particular girder design is chosen to the time a load carrying system is constructed on-site. Bridges employing girders having certain cross-sectional configurations also require cross frames to be coupled between adjacent girders in order to maintain sufficient structural stiffness of the load carrying system. These cross frames add to the expense, maintenance cost and labor of bridge installation.
Overall, there is increased desire for load carrying systems that can be more rapidly deployed at a relatively low cost. In certain applications, for example, pre-assembly of significant components of a load carrying system, such as a bridge deck and supporting girders, would provide for faster installation of a bridge system. It would also be advantageous to have a fabrication method for steel girders in which an individual girder pattern could be easily duplicated such that a series of matching girders may be formed.